Hydraulic drilling device



July '27, 1943. E, MERTEN 2,325,264

HYDRAULIC DRILLING DEVICE Filed Sept. 27, 1940 bq H15 Amm@ M Patented 'July 27;'1943 VHYDRAULIC Damme nevica A Eugen Merten, Houston, Tex., assignor to Shell Development Company, San Francisco, Calif., a corporation of Delaware Application September 27, 1940, Serial No. 358,585

.(Cl. Z55- 24) 4Claims.

This invention relates to hydraulically operated drilling devices. and pertains more particularly to a system wherein high pressures generated by the So-called water-hammer eilect are utilized for drilling purposes.

Although rotary methods haveheretofore been commonly applied for the drilling of deep wells,

y it has now been found that superior results may be obtained by impact drilling or by a combination of impact with rotary drilling. This is especially true in drilling through extremely hard rock formations and` in drilling relatively shallow boreholes, such as are used in seismic exploration, geochemical prospecting, etc.

It is, therefore, an object of this invention to provide a system wherein water-hammer elects or impulses are utilized for impacting a drill bit against earth formations.

It is also an object of this invention to provide a drilling system comprising a valve capable of suddenly stopping the iluid flow in a conduit to generate high pressure water-hammer eects.

It is also an object of this invention to provide a system wherein water-hammer impact drilling is combined with rotary drilling to secure optimum penetration effects.

It is also an object of this invention to provide a hydraulic impact drilling system comprising ilow equalizers for controlling the frequency of the bit impacts and for absorbing shocks and minimizing the shattering effects of water-hamhead equipment;

Fig. 2 is a diagrammatic cross-section view of another embodiment of an inside flow equalizer or shock` absorber; and

Fig. 3 shows diagrammatically a valve which may be used in the bit of Fig. 1.

The present system is especially useful as portable equipment in arid zones lacking in water, or

in drilling through ilssured formations causing excessive losses of drilling iluid, since it may be water which may be brought in a tank forming a part of the portable equipment.

Referring to Fig. 1, numeral 2 indicates a drill bit which may be of any desirable type or shape. The bit is attached to the lower end of a string of drill pipe or tubing Il), which extends to the surface. Means for imparting to the string i0 a rotational motion, either manually or by power machinery, as, for example, through a rotary table, may be used in a manner well known in the art. A pump 24 is used to circulate a liquid such as Water, brine or a suitable drilling fluid through the upper portion of the tubing i0, and is connected thereto by means of a conduit 28 provided with a valve 26, while a conduit 21 is used to return the liquid to the pump.

The bit 2 is aiiixed for axial motion within the enlarged lower cylindrical member 6 of the tubing I0, which tubing member 6 is provided with a bottom flange 4. The bit 2 has a cylindrical portion 8 provided at its upper end with a top flange 8a, adapted to iit slidably within the cylindrical member 6. A powerful spring 3 is wound around the cylindrical portion 8 of the bit, and is held between the ilanges 8a and 4, whereby the motion of the bit with regard to the tubing string is limited, and the bit is normally held in a raised position with regard to said tubing string. Openings Sa are provided to prevent any liquid leaking past anges 4 and 8a into the housing of the spring 3 from exerting any hydraulic effect opposing the compression of said spring.

The bit 2 may be provided with a passage I, through which the liquid circulating in the system of pump 24, conduits 21 and 28 and tubing iii may be passed into the borehole. The passage i is, however, normally closed by a plug 60, or a valve shown in Fig. 3, to be described hereinbelow. The conduit 21, connecting the -tubing string I0 to the low side of the pump 24 is pro-y vided, near said tubing, with a valve comprising a valve cage provided with perforations 63 and 64 for the iiow of the liquid in the conduit 21 as indicated by the arrow.

The valve cage 62 contains a ball valve 6I made of .rubber or other suitable resilient material. When the pressure differential generated by the liquid flow at the operating pump pressure reaches a predetermined value, the elastic ballvalv 6| is attened or deformed and -pressed against the bottom and walls of the valve cage, thus stopping the fiow of the liquid and causing a water-hammer effect as will be explained hereinbelow. 'Ihe hardness and resiliency, and the size of Ithe ball used for operations with a limited amount of valve 6|, are selected with consideration to the working pressure at which it is desired to operate the pump 24 to give an operative closure time for the valve structure.

'I'he tubing I0 is extended above the point of its connection with conduit 21 to a desired height in order to regulate the frequency of operation of the impact bit, and may be provided with an enlarged portion 65 comprising a flow equalizer to be described hereinbelow. 'I'he tubing I0 is provided at the top with a swivel or other suitable connection 66, whereby a liquid, originally held in ar tank 68 and' supplied therefrom to the pump 24 through a pipe 69, may be circulated in a closed circuit comprising pump 24, conduit 28, swivel $6, flow equalizer'i, tubing I0, and conduit 21 returning to the pump. The waterhammer pressures generated by the valve 6I62 are transmitted to the bit 2 through the liquid filling the tubing I therebetween, the plug or valve 60 normally preventing any escape and loss of the uidyto the borehole.

When said circulation of the liquid is established by starting the pump 24 and opening the valve 26, a certain pressure diiferential is created by the flow of the liquid through the relatively restricted orifices 63 and 64 between the space within tubing I0 upstream of said orifices, and

the space in conduit 21 downstream yof said orifice, said pressure differential being a function of the rate of flow in passages I0 and 63-64, respectively.

v The resilient ball 6I is selected of a compression strength such that it will close suddenly the orifices 64 when this pressure differential reaches a value corresponding to a predetermined fluid velocity in tubing I0 delivered by the pump 24, for example, it. per second, the valve 62 being in general adapted to close in a time period smaller than 2 L/u, wherein L is the length of the conduits between 4the flow equalizers I4 (to be described hereinbelow) and the valve 62, and u is the velocity of transmission of pressure waves in the liquid, which for water is in prac-l tice about 4200 feet per second.

It is known from hydraulics that when, under these circumstances, the flow of the circulation liquid is abruptly stopped by thev closure of the valve II', its kinetic energy is transformed into static pressure energy. The high pressure which is thus generated, and which is additional to the working pressure developed by the pump, produces the so-called water-hammer effect, and may be expressed by the following formula derived from the equation of conservation of energy:

vuc

wherein P is the maximum additional pressure produced by 'the closure of the valve II, u is the velocity of liquid in the tubing, u is the velocity of transmission of pressure waves in the liquid, w is the weight of a unit volume of the liquid, and g is the gravitational acceleration constant.

When P and w are in pounds, and v and u in feet per second, the above formula becomes P=63v, or, taking into consideration the elasticity of the water and of the tubing, as well as various losses, about 600 to 2000 lbs. per sq. inch for the device of the present invention at working pump pressures of from about 60 to 100 lbs.

per sq. inch.

'I'hese high additional pressures act to compress the spring 3 and to impact the bit 2 sharply against the formation to be drilled. Since, however, a water-hammer cycle consists of a high pressure period followed by 'a subnormal pressure period, both' the spring 3 and the valve ball 6I expand again during this latter period, therebyreturning the blt2 to its original position and opening the valve 62, after which the cycle is repeated.

, While the bit is being reciprocated against the formation, the` drill string may be caused to rotate by any desired means, whereby the cutting blade or blades of the bit are rotatably displaced with regard to the formation (substa'ntially only during periods between successive impacts), and a better rate'of penetration may be obtained.

As shown in Fig. 1, the drill pipe or tubing I0 is provided at any desired level Vabove the con"- duit 21 'with a plurality of annular internal funnel-shaped members I4, which may be attached,

by welding or in any other suitable manner, to one or more of the tubing stands forming the drill string. The members I4 constitute an inserving to form a -series of air chambers, ass

shown at I5.` It is known that air chambers are very effective as shock absorbers for waterhammer pressures in that part of the equipment which lies between an air chamber and the point of flow origin, without affecting said pressures inthat part of the equipment which lies belin permittingthe pump to work smoothly and therefore raising its efficiency, and in controlling the frequency of the water-hammer cycles by limiting the amount of1iquid which is aecelerated. If` desired, the diameter of the tubig stands comprising the internal flow equalizers I4 may be enlarged as shown at 65, so that the flow capacity of said stands may remain equal to that of the unobstructed stands. For purposes of control, the length of the tubing connected between flow equalizers and the bit may be varied, whereby the frequency of impacts is varied. In general, the frequency of impacts is a function of several factors. Thus, the cycle of each impact may be divided into three parts: first, the time necessary to accelerate the fluid .in tubing I0 to the velocity at which the valve 62 will close; second, the time during which the high pressure prevails on the bit and said valve remain closed; and third, the time necessary for the spring 3 to force the bit back to its normal position, driving the water which collected in the bit chamber up into the flow equalizer. The first period depends mainly on the pressure which the pump 24 can maintain in the flow equalizer, the amount of water between the internal and the external flow equalizers which has to be accelerated, the velocity to which it has to be accelerated before the valve 62 closes; and, finally, upon the size of orifices 63-64. The second period is short, and is equal to the distance between the internal flow equalizer and valve II divided by the Velocity of the elastic seance I l l 3.

Athus the passage I. Since the o'riiice 90 allows only a slowequalization of pressure, a]

operating frequency for the present system is, for example, 15 cycles per second. v

When the present system is operated for protracted periods of time and at high frequency, the air in the air-cushion spaces I may become dissolved in the water which is constantly and violently agitated in contact therewith, whereby' diameter of the tubing I0, whereby an annularv K air chamber 55 is formed betweenthe sleeve 53 and the member 5I. Water-'hammer pressure surges within the tubing I0 distend the sleeve 53 to a position shown on the left-hand side of l the drawing, whereby the same shock-absorbing eilect is obtained as described with regard to the device of Fig. 1.

As stated above, the member GIIQmay'be either a blind plug or a valve closing the passage Il throughout the periods of hemmen-drilling. A special arrangement of the valve 80, which permits said valve. to open when desiredto permit liquid circulation through the tubing or drill pipe I0, passage I, and up the borehole in -order to flush out theV cuttings and debris accumlated during the hammering or drilling period, is shown'in Fig-3. K

This valve comprises, within the tubing member 6, a housing 88, which may be of cylindrical shape and is screwed or attached to the bit 2 in a manner similar to that of the plug 60. The space within the housing 80 has a portion 81 in communication with the fluid within the tubing III-8 by means of passages 8|, and a portion 82 separated therefrom by means of uid-tight flexible diaphragms 83 and 84, made of a. resilient material such as rubber, the pressure-responsive area of diaphragm 83 being greater than that of diaphragm 84. A piston r85 is adapted to move within the housing 80 between said diaphragms. The piston 85 has attached thereto a stem 86, which passes through the diaphragm 84 and is attached thereto in fluid-tight manner, for example, by means of flanges 86a. The stem 86 terminates with a valve-head 88, which is adapted to close the passage I when the piston 85 is in its lowermost position. A spring 89 is provided to urge the piston 85 upwards. The space above the piston 85 is divided into two portions by a partition 9|, said portions being in communication with each other by means of a small orice or tube 90.

The space between the diaphragms 83 and 84 is filled with a suitable liquid, such as glycerine, water, etc., leaving preferably an air space shown at 92.

The eiective pressure areas of diaphragms 83 and 84 and the force of the spring 89 are selected so that at normal working pressures of the pump, the eiect of the pressure of the fluid in tubing I0 on the diaphragm 83 is able to overcome the pressure on the diaphragm 84 and the force of the spring 89. An equalization ilow takes place through orice 90 from the space above the partition 9| to the space below said partition, and forces the piston 85 downwards,

substantially constant pressure, which may be called the average pressure, prevails in space 9.2 during a hammering period, and maintains the passage I closed.

When, however, it is desired to 'flush out the cutitngs accumulating in the'borehole, the operator shuts oil.I the pump 24, or otherwise allows 'the pressure in tubing I0 to fall below a` predetermined value, whereupon the spring 8,9 overcomes the pressure-differential eiect of the diaphragms 83 and, and raises the piston 85, thus permitting the iiuid to pass through tubing III and 6 and passages 8l and I to the borehole. Considerable economies in operating iluid are thus realized by permitting iluid to circulate only through flushing periods, andl shutting it:

oi during hammering or drilling periods. lIn an embodimentvof the present invention successfully used in the ileld, drilling was carried out with average pressures of from 70 to 100 lbs. per square inch, and ushing with average pressures yoi about 40 lbs. persquare inch.

Misunderstood that the valve shown by numerals 8I- and 82 in Fig. 1 is not coniined tothe particular structures :shown in these figures, but

embraces anystructure `wherein a liquid ilow in a conduit system is abruptly stopped by resilient valve means in said conduit system, which l is caused to close in a suitably short time period at a predetermined pressure diierential created by said flow, thereby generating lhigh pressure water-hammer effects.

I claim as my invention:

end of said string and adapted for limited axial motion with regard thereto, spring means between said bit andsaid string regulating said motion, means for circulating a-liquid in a losed hydraulic circuit, said means comprising said string, a

pump, a first conduit in communication between the low side of said pump and said string, and a second conduit in communication between the high side of said pump and said string at a point spaced from said first conduit, and water-hammer means to reciprocate -said bitwith regard to said spring, said means comprising a restricted vpassage in said rst conduit and normally open resilient valve means in said passage responsive to a predetermined ilow pressure differential across said passage for suddenly closing said passage.

2. A hydraulic drilling system comprising a drill string, a drill bit normally sealing the lower end of said string and adapted for limited axial motion with regard thereto, spring means between said bit and said string regulating said motion, means for circulating a liquid in a closed hydraulic circuit, said means comprising said strong, a pump, a first conduit in communication between the low side of said pump and said string, and a second conduit in communication between the high side of said pump and said string at a point spaced from said iirst conduit, water-hammer means to reciprocate said bit with regard to said spring, said means vcomprising a restricted passage in saidflrst conduit and normally open resilient valve means in said passage responsive to a predetermined ow pressure diiierential across said passage for suddenly closing said passage, a iiuid passage through the bit, valve means normally closing said passage, and valve control means responsive to a substantial pump pressure drop for opening said valve.

1. A hydraulic drilling system. comprising a drill string, a drill bit normally sealing the lower 3. A hydraulic drilling system comprising a drillstring, a drill bit normally sealing the lower end of said string and adapted i'or limited axial motion with regard thereto, spring means between said bit and said string regulating said motion, means for circulating a liquid in a closed hydraulic circuit, said means comprising said string, a pump, a rst conduit in communication between vthe low side of said pump and said string, and a second conduit in communication between the high side of said pump and said string at a point spaced from said first conduit, water-hammer means to reciprocate said bit with regard to said spring, said means comprising a restricted passage in said first conduit and normally open resilient valve means in said passage responsive to a predetermined ilow pressure diierential across said passage for suddenly closing said passage, and at least one air chamber opening to said drill string between said rst and second conduit.

4. A hydraulic drilling system comprisingV a drill string, a drill bit normally sealing the lower end of said string and adapted for limited axial motion with regardI thereto, spring means between said bit and said string regulating said motion, means for circulating a liquid in a closed hydraulic circuit, said means comprising said .5 string, a pump, a nrst conduit in communication between the low side of said pump and said string, a second conduit in communication between the high side of said pump and said string at a point spaced from said first conduit, water-hammer 10 means to reciprocate said bit with regard to said spring, said means comprising a restricted passage in said nrst conduit and normally open resilient valve means in said passage responsive to a predetermined ilow pressure diierential across 15 said passage for suddenly closing said passage,

and at least one air chamber opening to said drill v EUGEN MER'I'EN. 

